Interstellar Interlopers, Coming in from the great beyond |
Interstellar Interlopers, Coming in from the great beyond |
Jun 28 2018, 04:09 AM
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#136
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Merciless Robot Group: Admin Posts: 8783 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Either that or just heated dust expanding and poofing out. The entire object was at a few degrees Kelvin for who knows how many millions of years before it entered our system.
-------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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Sep 2 2018, 02:26 PM
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#137
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Member Group: Members Posts: 684 Joined: 24-July 15 Member No.: 7619 |
A papers came out in May measuring the different between the in-bound and out-bound trajectories.
Sugggestions are that it has lost all of it's fine surface dust, so the venting gas is throwing out sand grain sized material, which is almost impossible to detect - so, it's a "dark comet" NON-GRAVITATIONAL ACCELERATION IN THE ORBIT OF 1I/2017 U1 (‘Oumuamua) DRAFT 13 pages https://www.spacetelescope.org/static/archi...3/heic1813a.pdf Non-gravitational acceleration in the trajectory of 1I/2017 U1 (‘Oumuamua) Published 24 pages http://www.ifa.hawaii.edu/~meech/papers/20...2018-Nature.pdf https://www.nasa.gov/feature/jpl/chasing-oumuamua |
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Sep 2 2018, 02:31 PM
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#138
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Member Group: Members Posts: 684 Joined: 24-July 15 Member No.: 7619 |
Back to being a comet? There appears to have been some outgassing after all ... I initially argued that they should check for a change in speed because of fragmentation- if a fragment breaks off a comet around perihelion, the period of highest stresses, then the fragments carry slighly different velocities, AND you expose fresh ices. That also raised the interesting possibility is that if Oumaumau was accellerated, the small fragment should be decellerated, and might be on a solar capture orbit- analagous to models where Neptune can capturing Triton if it starts as a dual-KBO, one is ejected, the other is captured. However, the paper finds that a fragment would have to be about 1% of the size, and nothing that big was detected. |
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Nov 15 2018, 02:30 AM
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#139
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Senior Member Group: Members Posts: 2082 Joined: 13-February 10 From: Ontario Member No.: 5221 |
New Spitzer results published, better constraints on size: http://iopscience.iop.org/article/10.3847/...881/aae88f/meta
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Nov 15 2018, 02:57 AM
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#140
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Member Group: Members Posts: 684 Joined: 24-July 15 Member No.: 7619 |
New Spitzer results published, better constraints on size: http://iopscience.iop.org/article/10.3847/...881/aae88f/meta Interesting about total mass and aspect ratio. Given the recent papers providing numbers based on solar photon acceleration suggesting high surface area, and remembering how papers about Pluto discussed how low pressure and cryo temperatures drives the formation of multi-meter sized ice crystals, what forms of ice (Ice II, III, IV etc) are stable in the hard vacuum of interstellar space? Perhaps we saw the largest snowflake ever... |
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Nov 15 2018, 11:23 PM
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#141
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Senior Member Group: Members Posts: 2346 Joined: 7-December 12 Member No.: 6780 |
This phase diagram suggests orthorhombic ice XI.
But more exotic forms of water ice may exist. And clathrates are always an option to be considered at these low temperatures and mixtures of volatile compounds in interstellar space. But any volatiles must have been mostly protected by a non-volatile layer. Otherwise, obvious cometary activity would have been observed. |
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Feb 2 2019, 01:15 AM
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#142
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Member Group: Members Posts: 684 Joined: 24-July 15 Member No.: 7619 |
This phase diagram suggests orthorhombic ice XI. But more exotic forms of water ice may exist. And clathrates are always an option to be considered at these low temperatures and mixtures of volatile compounds in interstellar space. But any volatiles must have been mostly protected by a non-volatile layer. Otherwise, obvious cometary activity would have been observed. Newer simpler explantion - 'Oumuamua broke up on the far side of the sun, what we saw was a spinning dust cloud. 1I/‘OUMUAMUA AS DEBRIS OF DWARF INTERSTELLAR COMETTHAT DISINTEGRATED BEFORE PERIHELION https://arxiv.org/pdf/1901.08704.pdf |
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Feb 18 2019, 04:11 PM
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#143
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Senior Member Group: Members Posts: 2082 Joined: 13-February 10 From: Ontario Member No.: 5221 |
And another theory: https://arxiv.org/abs/1902.04100
A sort of 'fractal snowflake' of incredibly low density (but completely natural!) would also explain the observed properties. |
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Feb 19 2019, 03:17 PM
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#144
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Junior Member Group: Members Posts: 68 Joined: 27-March 15 Member No.: 7426 |
The 'fractal snowflake' interpretation is intriguing. There seem to be problems with it, though. The authors of the paper mention some of these.
It seems difficult to understand how such a flimsy object could withstand the forces that wrenched it from its star and sent it our way. Even the relatively rapid rotation of Oumuamua would seem to threaten the continued existence of such a delicate structure. Then, too, it's assumed that a 'fractal snowflake' would have formed beyond the snowline in its system. It seems possible that it would have begun to melt, and come apart when it passed near the Sun, on its journey through our solar system. |
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Sep 12 2019, 10:07 AM
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#145
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Newbie Group: Members Posts: 17 Joined: 8-September 15 Member No.: 7773 |
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Sep 12 2019, 12:22 PM
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#146
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Member Group: Members Posts: 684 Joined: 24-July 15 Member No.: 7619 |
The 'fractal snowflake' interpretation is intriguing. There seem to be problems with it, though. The authors of the paper mention some of these. It seems difficult to understand how such a flimsy object could withstand the forces that wrenched it from its star and sent it our way. Even the relatively rapid rotation of Oumuamua would seem to threaten the continued existence of such a delicate structure. Then, too, it's assumed that a 'fractal snowflake' would have formed beyond the snowline in its system. It seems possible that it would have begun to melt, and come apart when it passed near the Sun, on its journey through our solar system. Perhaps another degree of freedom is the rotational energy-think of "a snowglobe of fractal snowflakes", or a "cold synestia". It should look something like Saturn's moon Methone, a gravitationally bound snowstorm. Instead of a collision, imagine a slow YORP effect spin upon a rubble pile asteroid, like Ryugu or Hyabusa, until they are disks or a torus. Finally, if you imagine a body that is a rubble pile composed of rock cemented by ice. If the object has not had time to evolve a dark comet-style surface crust, then you might have a cometary body with a gravel surface. That might allow significant heat conduction into a porous interior; either from direct rock-to-rock conduction or by sublimated surface ices in gas form diffusing into the cold porous interior and refreezing. Interesting to think about what happens for an object of rock-cemented-by-ices; if the object warms uniformly. Once it reaches ice sublimation throughout the interior, additional warming could create a 3-dimensional fluidized bed of rock granules. |
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Sep 12 2019, 12:39 PM
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#147
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Senior Member Group: Members Posts: 2082 Joined: 13-February 10 From: Ontario Member No.: 5221 |
Here we go again!
Looks to be a comet this time, with an even higher eccentricity! And this time it's still on the way in, and should be visible for many months! |
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Sep 12 2019, 02:52 PM
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#148
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Member Group: Members Posts: 124 Joined: 20-April 05 Member No.: 291 |
Most impressive is that it wasn't an automated survey or space telescope that found it - but an amateur comet hunter with a home built .65 m telescope! Comet should be visible for a year in large scopes.
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Sep 15 2019, 03:48 AM
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#149
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Junior Member Group: Members Posts: 23 Joined: 28-September 17 From: Huntsville, Alabama Member No.: 8258 |
First visual spectrum of C2019/Q4 http://www.iac.es/divulgacion.php?op1=16&a...0wY3wWUq58FS8OQ
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Sep 15 2019, 09:30 AM
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#150
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Merciless Robot Group: Admin Posts: 8783 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Topic title changed to plural.
-------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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